1. Field of the Invention
This invention relates to air bearing sliders for use in disk drives, and more particularly, to air bearing sliders that are less sensitive to mask misalignments.
2. Description of Related Art
Conventional magnetic disk drives refer to information storage devices that store data on at least one rotatable magnetic media (or disk) having concentric data tracks. Conventional disk drives include a spindle on which the disks are mounted, a spindle motor that spins the disks when the drive is in operation, one or more read/write heads that perform the actual reading and writing of data, a second motor that positions the read/write heads over the disks, and controller circuitry that synchronizes read/write activities and transfers information to and from the computer or data processing system. A read/write head may include a magnetic transducer (also referred to as a read/write transducer) for reading and writing data on the various tracks. The read/write transducer is typically mounted or integrally formed on an air bearing slider. The air bearing slider supports the read/write transducer above the recording media and adjacent to the data tracks during reading and writing operations of the drive.
In magnetic recording technology, it is continually desired to improve the areal density at which information can be recorded and reliably read. One factor that limits the recording density of a magnetic disk drive is the distance between the read/write transducer and the magnetic media. This distance is often referred to as the "fly height" of the air bearing slider. As the area density of the magnetic media is increased, smaller fly heights are required so that the read/write transducer can distinguish between the magnetic fields emanating from closely spaced regions on the magnetic media. Accordingly, air bearing sliders are typically designed to fly the air bearing slider as close as possible to the magnetic media while avoiding physical impact with the magnetic media.
Various factors are known to affect the fly height of an air bearing slider. For example, the fly height of an air bearing slider is affected as the actuator arm is moved radially across the disk to access the various data tracks. This is due to differences in linear velocity of the disk at differing radii between the inner-diameter (ID) and the outer-diameter (OD) of the disk. Additionally, an air bearing slider may experience changes in fly height due to variations in skew, roll, and crown of the air bearing slider. The altitude sensitivity of an air bearing slider may also affect the fly height. As the altitude increases, the fly height drops corresponding to the drop in atmospheric pressure. Furthermore, variations in the physical characteristics of an air bearing slider that results from manufacturing tolerances may also affect the fly height. For example, the misalignment of masks used to form the various surfaces may vary the physical characteristics of the air bearing slider.
One prior art air bearing slider is a negative pressure air bearing slider having two etch depths formed by a two step etching process, as shown in FIG. 1. FIG. 1 illustrates an air bearing slider 100 having a support structure 140 (also referred to as a slider body), a first etch surface including a leading step region 120 and a trailing step region 121, a second etch surface including a negative pressure region 150, and an air bearing surface including leading pads 130 and 131 and a trailing pad 132. The depth of each etch surface is measured from the air bearing surface of air bearing slider 100.
The leading step region 120 and trailing step region 121 are formed by a first etch and therefore referred to as the first etch surface. The first etch may be a shallow etch of about 0.11 microns. The leading step region 120 has two side rails that are joined together at leading edge 141 of slider body 140 and extend toward trailing edge 142 of slider body 140.
The pocket defined by the two side rails of leading step region 120 is referred to as negative pressure region 150 and is formed by a second etch. The second etch may be optimized anywhere between 0.5 microns and 5.0 microns to minimize the altitude sensitivity of air bearing slider 100. Typically, the second etch depth refers to the first etch depth plus a delta value such that the area defined as the second etch surface is actually etched during the first and second etch steps. Although this prior art approach reduces the altitude sensitivity of air bearing slider 100, it does not reduce mask misalignment sensitivities of air bearing slider 100 that may also affect the flying height.
Another prior art approach uses a three step etching process to form three etch surfaces. FIGS. 2A-2B illustrate a three etch depth air bearing slider. According to FIGS. 2A-2B, the air bearing slider includes four transverse pressure contour (TPC) pads 222 and a negative pressure pad 226. The TPC pads 222 are defined by a face 234 for creating a gas bearing effect, a generally U-shaped TPC section 228 including a constant depth step bearing along each side edge 236 of face 234 and a constant depth step along leading edge 238 forming a converging compression inlet 232. Thus, the gas bearing contour of TPC pad 222 is defined by two parallel planes created by two different etch steps with a slight off-set.
The negative pressure pad 226 is defined by a substantially planar surface which contains a recess 240 open at the trailing end 225. The negative pressure pad 226 may also include one or more bearing faces 242 at a height approximately that of faces 234 and TPC pads 222 for creating a gas bearing effect. Recess 240 is open along the trailing edge 241; that is, substantially ambient.
The ambient pressure reservoir 230 defines a cavity 244 having a depth and configuration sufficient to maintain substantial ambient pressure in the cavity during movement of the disk. Furthermore, ambient pressure reservoir 230 includes a non-tapered (non-stepped, non-convex) inlet along a leading edge 223 so as to inhibit the generation of gas bearing effects created by compression of inlet gas.
In order to ensure cavity 244 creates an ambient pressure reservoir 230, cavity 244 must be etched deep enough to ensure ambient pressure. According to this slider design, the etch steps used to form the U-shaped TPC section 228 and recess 240, alone or in combination, are not deep enough to form cavity 244. Thus, the prior art design shown in FIGS. 2A-2B requires three etch steps to form the three etch surfaces. One drawback of this slider design is that an air bearing slider manufactured with a three step etching process is more costly to manufacture than the same slider if manufactured with a two step etching process.